Test which items are activated when pressing Enter or Return

Test which items are activated when pressing Enter or Return

The ViewState struct gets a new bool member to indicate if the selected
items should have been activated after the last event or not. One could
argue that adding a bool parameter to the constructor is not optimal,
but I think adding an enum is not really worth the effort because the
struct is not used outside this unit test. Moreover, I could not think
of a good name for the enum type and its values.
(cherry picked from commit 307cca7b31b998fb7e8af0478a8e97e53bdc059c)